In a gas turbine, a gas is compressed through successive stages in a compressor and mixed with fuel in a combustor. The combination of gas and fuel is then ignited for generating combustion gases that are directed to turbine stages to produce rotational motion. The turbine stages and compressor stages typically have stationary or non-rotary components, e.g., vanes, that cooperate with rotatable components, e.g., rotor blades, for compressing and expanding the operational gases.
Fluid leakage between stages reduces overall gas turbine engine performance and efficiency and therefore, interstage seals are provided to reduce such leakage. In general, fluid leakage is reduced when a gap between the seal and a rotor assembly is minimized. Labyrinth seals have been used to effect a seal between stages at different pressures in gas turbine engines. Such seals generally comprise two principal elements, i e, a rotatable seal and a static seal. The static seal comprises an annular member. The rotatable seal, as viewed in cross section parallel to the axial length of the engine, frequently has rows of thin labyrinth fingers or teeth extending radially from a relatively thicker base. The teeth of the rotatable seal extend radially to a location adjacent the static seal.
It is desirable to have sufficient contact between the labyrinth teeth and the static annular member such that a seal is formed between those components. However, if excessive contact or pressure between the labyrinth teeth and static annular member occurs, then either the teeth or annular member may be damaged. Conversely, insufficient contact between those components results in a failure of the seal. Thus it is desirable to maintain the rotatable and static portions of a labyrinth seal in an appropriate degree of contact with each other.